Crabs crowd the streets on Australia's Christmas Island. (Photo: Di Masters)Watch where you're driving, folks: Australia's Christmas Island annual crab migration can start any time between now and the end of the year. As the rainy season begins, more than 40 million of the adult red crabs begin the 9-kilometer trek (about 5.5 miles) from the middle of the island to the Indian Ocean to breed and spawn.
One problem: the side-stepping crustaceans have no regard for the rules of the road, which means a lot of work for the Australian national parks department to set up safe passage for the migrating hordes.
Park rangers, shown at work in the video below, set up temporary fencing, which directs the crabs to underpasses below the streets. For roads without detours, workers employ rakes to sweep jaywalking crabs off the street. Signs also warn drivers along certain roads.
But it's still a hazardous route, and there will be the inevitable road kill during the difficult five-day journey. At points during the month-long movement, the roving creatures cover the area with a crimson tide of claws.
The males are the advance team at the beach. They dig burrows for the females, who arrive five to seven days later. After breeding, the females stay in the burrows for another two weeks or so, laying eggs and waiting for them to develop, Australian Geographic explains.
The females time the release of the eggs to high tide, when the eggs hatch and are washed out to sea. After about a month in the ocean, the baby crabs come ashore and start their own march home, according to the Parks Australia website.
The incredible sight, described as "one of the wonders of the natural world," takes place on an island with such a variety of species that it's known as the "Galapagos of the Indian Ocean," according to the island's tourism website.
Amazingly, this isn't the only crab migration that's been caught on camera. Hermit crabs, millions of them, were filmed on St. John in the U.S. Virgin Islands as they created a carpet of crustaceans on the beach.